Geologic Map of the
Mound Springs Quadrangle,
Lincoln, Otero, Sierra, Socorro Counties, New
Mexico
By
Love, David; Allen, Bruce; Myers, Robert
June, 2007
New Mexico Bureau of Geology and Mineral Resources
Open-file Digital Geologic Map OF-GM 163
Scale 1:24,000
This work was supported by the U.S. Geological Survey, National Cooperative Geologic
Mapping Program (STATEMAP) under USGS Cooperative Agreement 06HQPA0003
and the New Mexico Bureau of Geology and Mineral Resources.
New Mexico Bureau of Geology and Mineral Resources
801 Leroy Place, Socorro, New Mexico, 87801-4796
The views and conclusions contained in this document are those of the author and
should not be interpreted as necessarily representing the official policies,
either expressed or implied, of the U.S. Government or the State of New Mexico.
(BDA_MSMUdraft of 12/12/06)
DESCRIPTION OF MAP UNITS, MOUND SPRINGS QUADRANGLE
CENOZOIC EARATHEM
NEOGENE
Valley -floor deposits
af
Artificial fill (Historic) — Dumped fill and areas affected by human disturbances;
mapped where deposits or extractions are areally extensive. Commonly includes
earth dams in alluvial drainages, borrow pits for road construction and raised roads,
and large sand and gravel quarries where original deposits can no longer be
interpreted.
Qa
Valley-floor alluvium, undivided young deposits (Holocene to uppermost
Pleistocene) — Very pale brown to light reddish-brown (10 YR 8/3 to 5YR 6/4),
inter-channel dominantly fine-grained (fine sand, silt, and clay) alluvium and
anastomosing small channels of poorly to moderately sorted, unconsolidated pebbly
sand with local gravel bars. Relief between channels and alluvial valley floors is
typically less than 1 m. Locally buries older gravel bars, former terrace deposits
(Qpil), and accumulations of gypsum. Soil horizons are not evident. In bedrock
areas, deposit is less than about 3 m thick. In bajada areas, deposit is more than 10
m thick and probably caps similar bolson fill.
Qag
Thin alluvium in drainages crossing thick gypsum deposits (Holocene to upper
Pleistocene?) — Unconsolidated pale brown to light reddish brown (10 YR 8/3 to
5YR 6/4) fine-grained sand to clayey silt alluvium and loess with angular clasts of
gypsum crust. Rarely contains pebbles derived from the Oscura Mountains. Locally
fills dissolution-related small valleys developed in gypsum megamounds.
Commonly less than 1 m thick, but ranges to more than 4 m thick.
Qc
Colluvium (Holocene to uppermost Pleistocene) — Unconsolidated to very
poorly consolidated, angular blocks of sandstone and minor limestone resting on
slopes below bedrock ledges. Colors similar to underlying units and blocks. Matrix
includes mudstone and rare pedogenic gypsum crust. Deposits range from less than
1 m to about 3 m thick.
Qe
Eolian sand (Holocene to uppermost Pleistocene) — Unconsolidated to very
poorly consolidated, moderately to well sorted, very pale brown (10 YR 7/3) sand.
Forms extensive sheets and low dunes along the northeast sides of drainages.
Common as coppice dunes beneath mesquite (Prosopis glandulosa) thickets.
Deposits range from less than 1 m to about 3 m thick.
Spring-related deposits
1
Qgs
Gypsum spring deposits as spring mounds (Holocene to upper Pleistocene?) —
Well to semi-consolidated, conical to domal, white (N9), gray (10 YR 8/2), to light
tan (10 YR 8/3) gypsum deposits surrounding central spring-orifice craters. Eolian
siliceous-sediment accumulations and finely disseminated organic matter form a
minor component of some mounds, although the surfaces of a few mounds contain
significant amounts of eolian silt and sand. Gypsum precipitates generally consist of
scattered, sand-sized lenticular grains set in a cryptocrystalline matrix, and may
contain up to several weight percent carbonate minerals. Spring mounds range from
less than 1 to more than 6 m high and from 12 to more than 100 m in diameter.
Inactive craters are nearly filled with pale brown fine sand, silt, and clay deposited
as loess and extensively burrowed by small mammals. Crater rims and upper slopes
of mounds commonly are unburrowed consolidated gypsum crusts underlain by
rock gypsum. Lower slopes commonly have discontinuous eolian and alluvial
cover. Subsurface deposits of active spring mounds are moist beneath gypsophilous
vegetation and powdery evaporite efflorescence. Gypsum precipitates on the
substrate of active pools are largely silt- and fine-sand-sized lenticular and hemibipyramidal crystals. Consolidated gypsum commonly is broken into sub-meter
columnar polygons with vertical and anastomosing fractures filled with banded
gypsum and minor calcium carbonate. Iron and manganese staining of consolidated
gypsum is locally apparent. Deposits overlie valley floor alluvium and/or older
gypsum deposits.
Qgmm Gypsum megamounds and associated, down-gradient gypsum spring deposits
(Holocene? to upper Pleistocene) — Consolidated light brown to gray to white
gypsum deposits forming extensive upland areas above alluviated drainages, and
associated, generally thick, distal accumulations. Uppermost ~1 m is generally a
consolidated gypsum crust broken into sub-meter columnar polygons, further
broken into cobbles and sub-horizontal plates 2-5 cm thick at the surface. In some
areas the indurated surface crust is underlain by up to several decimeters of
relatively loose, powdery gypsum silt and sand. Loess and thin alluvium locally
covers the crust. Beneath the surface where exposed in artificial excavations and in
sinkholes are crudely bedded semi-consolidated and consolidated gypsum layers.
Estimated to be as much as 14 m thick.
Qgmk
Karst features developed in eastern megamound, and adjacent areas
(Holocene) — Consolidated light brown to gray to white gypsum deposits
in the immediate vicinity of sinkholes that are up to 7 m deep and 100 m
across, oriented along NW and two parallel NE trends and locally in N-S
trends. The floors of several of the sinkholes contain vertical to subhorizontal dissolution fractures and caves of unknown extent.
Observations following an intense rainfall event indicate that large
quantities of surface runoff flowing into the sinkholes disappears
immediately into these subterranean passages. Other sinkholes have
become plugged with eolian loess and alluvium and some are nearly filled.
2
Qss
Alluvium and saline-spring-affected deposits (Holocene to upper Pleistocene)
— Unconsolidated to partially consolidated, light brown to gray and greenish gray,
structureless to crudely bedded sand, silt, and clay cemented with gypsum and other
evaporites associated with shallow groundwater adjacent to and northwest of Salt
Creek.
Piedmont alluvial deposits
Qpy
Piedmont stream channel and floodplain alluvium (Historic and Holocene) —
Unconsolidated light brown, light reddish brown, reddish brown and gray-brown
sand, silt, and clay with local concentrations of pebble to boulder gravel in bars and
riffles in proximal to medial alluvial-apron landscape positions. Pebbles are
subangular to rounded with more durable siliciclastic types farther from mountain
slopes, and locally-derived sandstones, limestones, and igneous rocks closer to
mountain fronts. Color and composition of the sandy and finer alluvium depends on
sources upslope. For example, sediments derived from the Bursum Formation
pediment commonly are maroon pebbly sand and silt. Pedogenic calcium carbonate
accumulation reflecting soil development locally reaches Stage I. The unit
commonly buries older layers on the distal piedmont slope, but is inset against older
piedmont alluvial units in the proximal and medial piedmont. Discontinuous arroyo
channels dissect the piedmont alluvium locally. Thickness estimated to be less than
10 m.
Qpyd
Qpi
Piedmont, distal foot-slope apron, fine-grained alluvial deposits
(Holocene) — Unconsolidated light brown, light reddish brown, reddish
brown and gray-brown sand, silt, and clay with local concentrations of
pebbles and eolian loess. Decrease in slope and fewer channels from Qpy
upslope to Qa downslope.
Piedmont alluvial deposits, undivided intermediate levels (Historic to middle
Pleistocene) — Light reddish brown (5YR 6/4 and other colors), poorly to
moderately sorted, unconsolidated fine- to coarse-grained sand and gravel. Medial
and proximal deposits contain some boulders. The tops of these deposits are
extensive, nearly planar surfaces that are abandoned by inset channels and
floodplains of Qpy. Sheet-wash and eolian processes may still take place. Range in
ages shown by range in soil horizon development from none to stage I pedogenic
calcium carbonate. Thicknesses vary from 3-4 m near apexes to less than 1 m
(often less than 0.3 m as they commonly grade to floodplain levels) at their distal
margins.
Qpif
Piedmont, intermediate level, fine-grained alluvial deposits (Holocene
to upper Pleistocene?) — Unconsolidated pale brown, fine sand, silt, and
clay deposited as alluvium and possibly loess forming broad planar
3
sloping surfaces in western part of quadrangle and local valley fill in
northeast part of quadrangle. Overlies low, gravelly terraces in a few
places, but does not have soil horizons developed. At least 3 m thick.
Qpifs
Piedmont, intermediate level, erosional scarps in fine-grained
alluvial deposits (Holocene) — Partially eroded scarps in
unconsolidated, pale brown, fine sand, silt, and clay forming at
eastern and southeastern edges of Qpif. From 0 to 3 m thick.
Qpil
Piedmont and alluvial-fan deposits (Holocene to upper Pleistocene) —
Pale brown to light reddish brown (10 YR 8/3 to 5YR 6/4), poorly
exposed, poorly to moderately sorted, unconsolidated pebbly to cobbly
sand. Deposit surfaces are more than 1 m above local base level along
active piedmont drainages, continue to be more than 3 m above local base
level upstream. Soils are weakly developed and exhibit Stage I+
pedogenic carbonate morphology. This unit probably includes two distinct
kinds of deposits that occupy the same landscape position. Some of these
gravelly deposits are exhumed terrace deposits; others are late Holocene
alluvial fan deposits. Estimated to be 3 to 5 m thick.
Qpih
Piedmont and Alluvial-fan deposits (Pleistocene) — Light reddish
brown (5YR 6/4), unconsolidated to moderately consolidated sand and
gravel. Gravels consist of subangular to subrounded limestone, granitic
and metamorphic, and red sandstone rock types. Stable surface of deposit,
where not deeply dissected on rounded and planar divides between 5 and
12 m above adjacent channels, exhibits well developed soils with Stage
III+ pedogenic carbonate morphology. Deposits commonly are more than
12 m thick.
QTp
Piedmont and Alluvial-fan deposits of bolson fill (Neogene) —In
subsurface cross section only, south of range-bounding fault. Light reddish
brown (5YR 6/4), unconsolidated sand, mud, and gravel to consolidated
sandstone, mudstone and conglomerate. Pebbles consist of subangular to
subrounded limestone, granitic and metamorphic, and red sandstone rock
types. According to modeled gravity profile across southern Oscura
Mountains (Peterson and Roy, 2005) piedmont and alluvial fan deposits of
northern Tularosa basin may be at least 2.3 km thick.
PALEOGENE
Ti
Diabase dikes (probably upper Oligocene) — Dark gray to greenish gray mafic
dikes exhibiting diabasic texture of plagioclase and augite. Dikes follow east-west
vertical faults and fractures developed in Paleozoic sedimentary rocks. Dikes and
wall rocks of Bursum Formation have minor copper oxide and copper carbonate
4
(malachite) mineralization revealed in numerous prospect pits. Dikes range from
less than 1 to 7 m wide.
MESOZOIC ERATHEM
Kd
Dakota Formation (Upper Cretaceous [Cenomanian]) —Unit not exposed in
quadrangle; in cross section only. Consists of white, pale gray, and yellow crossbedded coarse-grained sandstone and conglomeratic sandstone deposited in fluvial
and marine environments. 55 m thick east of Mound Springs quadrangle (Arkell,
1986).
Trm
Moenkopi Formation (Middle Triassic [Anisian]) —Unit not exposed in
quadrangle; in cross section only. Consists of grayish red to maroon, poorly sorted,
cross-bedded micaceous litharenites, mudstones, and intraformational
conglomerates. The Moenkopi Formation is 91 m thick at Bull Gap east of Mound
Springs quadrangle (Lucas, 1991).
PALEOZOIC ERATHEM
PERMIAN
Pag
Artesia Group: Grayburg, Queen, Seven Rivers, Yates and Tansill formations,
undivided (Middle Permian [Guadalupian]) —Unit not exposed in quadrangle;
in cross section only. Consists of red to orange to light gray, fine- to very finegrained sandstone, siltstone, gray limestone, and evaporititic gypsum. The Artesia
Group is estimated to be 0 to 100 m thick in the northern Tularosa basin and shown
as 100 m thick in cross section.
Psa
San Andres Formation (Lower Permian [Leonardian-Guadalupian]) —Unit
not exposed in quadrangle; in cross section only. Consists of gray marine limestone,
interbeds of gray marine shale, evaporitic gypsum, and beds of light gray to
yellowish fine sandstone. Limestone units are planar over several km and exhibit
decimeter scales of cyclic bedding. The San Andres Formation is shown to be 213
m thick in the cross section, but ranges from 140 to 250 m thick in the Chupadera
Mesa area (Broadhead and Jones, 2004).
Pg
Glorieta Formation (Lower Permian [Leonardian]) —Unit not exposed in
quadrangle; projected in cross section only. Consists of thick-bedded, light gray to
yellowish fine sandstone with interbeds of gray marine limestone. It commonly
interfingers with the overlying San Andres Formation and resembles sandstone in
the underlying Yeso Group. The Glorieta Formation is estimated to be about 30 m
thick in the southern Oscura Mountains, but it thins to the south and may range
from 0 to 100 m thick according to Broadhead and Jones (2004).
5
Pyt
Yeso Group: Torres, Canas, and Joyita formations undivided (Lower Permian
[Leonardian]) — Base of unit (Bachman's upper Yeso Formation) was mapped in
the southern Oscura Mountains at the transition from pale red siliciclastic beds
below to dolomitic limestone, yellowish green shale, and gypsum above (see
Bachman, 1968). This transition is not exposed on the Mound Springs quadrangle.
The unit is present at the surface as a north-south ridge in the northwestern part of
the map area, where it contains poorly exposed bedded gray gypsum and yellowish
gray siltstone, and resistant, medium-bedded light gray limestone and yellowish
brown sandstone interbeds. Estimated by Bachman (1968) to be 435 m thick. To
northeast in the subsurface the Torres formation is as much as 1067 m thick and
contains salt as well as anhydrite (Broadhead and Jones, 2004). The overlying
Canas and Joyita formations are about 100 m thick.
Pya
Yeso Group, Arroyo de Alamillo Formation (Lower Permian [Leonardian]) —
Previously miscorrelated to Mesita Blanca Sandstone but recently described as the
Arroyo de Alamillo Formation by Lucas and others (2006). Base of formation
mapped at base of meter-scale ledges of ripple-crosslaminated sandstone or local
conglomeratic sandstones with colors distinctly different (2.5 YR 4/2; 5/2; 5/6)
from underlying Abo Formation. Overlying beds composed of thin-bedded, finegrained sandstone, pebble conglomerate, and siltstone. Trace fossils common. Top
of formation is not exposed in the map area. Weathers weak red (10 R 5/3), with
darker weak red (2.5 YR 4/2 to 5/3) mudstone with mudcracks. Estimated to be 50
m thick in the southern Oscura Mountains. Exposed in northwestern and northcentral part of quadrangle on east side of Red Hill.
Pa
Abo Formation (Lower Permian [Wolfcampian]) — Base of unit mapped at
poorly exposed change from brownish maroon of Bursum Formation to redder (2.5
YR 5/4; 4/3) sandstone and mudstone typical of Abo Formation farther north in
central New Mexico. Unit is more mature (less arkosic) than underlying beds in the
Bursum Formation, and consists largely of a basal sequence of poorly exposed
mudstone, grading up to fine-grained sandstone and mudstone at the top. Sandstone
and conglomerate units are commonly lenticular in distinct channels. Unlike Abo
Formation farther north, minor thin limestone beds and limestone-clast
conglomerates are present throughout. Limestones do not have recognizable
macrofossils, and some appear to have been calcareous soils. A distinctive bed of
red, ripple-crosslaminated fine-grained sandstone containing pods and stringers of
similarly crosslaminated dolomitic calcarenite is present near the top of the Abo
Formation in the area. In general, unit weathers red and pale reddish brown with
local white and pale green oxidation-reduction spots. Estimated to be about 41 m
thick on Red Hill.
lPb
Madera Group, Bursum Formation (Pennsylvanian-Permian [Virgilian and
Wolfcampian (?)]) — Base of unit mapped at change from fossiliferous gray and
yellowish gray limestone and greenish gray shale of top of Atrasado Formation to
reddish brown and maroon shale, siltstone, sandstone, and conglomerate. Coarsegrained units are arkosic. Siliciclastic clasts in conglomerate range to 20 cm in
6
diameter and consist of reddish gray, salmon, and weak red (10 R 4/2, 10R 6/1, 10R
5/6) Precambrian metarhyolite porphyries, quartzites, granite gneisses, and cherts in
an arkosic dark reddish gray sandstone matrix (10 R 4/1-4/2). Siltstone and shale
commonly are maroon, but may also be glauconitic green. Several gray to yellowish
gray to maroon ledges of limestone and/or limestone conglomerate form parallel
bands along the outcrop belt, but do not contain macrofossils. The Bursum
Formation is estimated to be on the order of 254 m thick or more in the southern
Oscura Mountains and the Mound Springs quadrangle.
lPma
Madera Group, Atrasado Formation (Upper Pennsylvanian [Missourian and
Virgilian]) — Base of unit not exposed in quadrangle. Kues (2001) summarized
regional correlations of Pennsylvanian strata in New Mexico, and concluded that
the formation-rank names Gray Mesa and Atrasado, respectively, should be used
rather than the informal "lower member" (~Desmoinesian) and "upper member"
(~Missourian-Virgilian) division of the Madera used by Bachman (1968) in the
Oscura Mountains. Consists of gray and greenish gray shale, reddish brown and
brown silty micaceous shale (10 YR 5/3), glauconitic sandstone, crossbedded,
quartzose to arkosic sandstone and pebbly sandstone, and gray, fossiliferous
(marine) limestone and calcareous shale. Limestone units are planar over several
km and exhibit several scales of cyclic bedding. The Atrasado Formation is
estimated to be 480 m thick in the southern Oscura Mountains.
lPmg
Madera Group, Gray Mesa Formation (Middle Pennsylvanian [AtokanDesmoinesian]) —Unit not exposed in quadrangle; in cross section only. Consists
of gray marine limestone and interbeds of gray marine shale. Limestone units are
planar over several km and exhibit several scales of cyclic bedding. The Gray Mesa
Formation is estimated to be 124-140 m thick in the southern Oscura Mountains.
lPs
Sandia Formation (Lower Pennsylvanian [Atokan]) —Unit not exposed in
quadrangle; in cross section only. Consists of gray, brown, and pink conglomeratic
coarse sandstone, gray micaceous shale, and gray and brown fossiliferous marine
limestone. It is estimated to be 76-128 m thick in the southern Oscura Mountains.
CO
Cambrian and Ordovician formations, undivided (Upper Cambrian to middle
Ordovician) —Units not exposed in quadrangle; in cross section only. Consists of
dark brown to gray calcareous sandstone of Bliss Formation; olive to gray sandy
dolomite of El Paso Dolomite; and gray crystalline dolomite and interbeds of gray
marine shale of Upham Dolomite member of the Montoya Dolomite (see Bachman,
1968). Composite thickness in cross section is about 100 m thick in the southern
Oscura Mountains.
pCg
Metamorphic and Intrusive rocks (Upper Proterozoic) —Unit not exposed in
quadrangle; in cross section only. Consists of gray and pink granite, granite gneiss,
and dark greenish gray diorite. Exposed in major uplifts of Oscura, Mockingbird,
and northern San Andres Mountains. Found as cobble-to-boulder-sized inclusions
7
in Paleogene diabase dikes in quadrangle, as clasts in Bursum Formation, and as
clasts in Quaternary piedmont deposits.
References Cited
Arkell, B.W., 1986, Stratigraphy of western part of Sierra Blanca Basin, in J.L. Ahlen
and M.E. Hansen, eds., Southwest Section of AAPG Transactions and Guidebook of
1986 Convention, Ruidoso, New Mexico: New Mexico Bureau of Mines and Mineral
Resources, Socorro, p. 73-76.
Bachman, G. O., 1968, Geology of the Mockingbird Gap quadrangle, Lincoln and
Socorro Counties, New Mexico: U.S. Geological Survey, Professional Paper 594-J, 43 p.
Broadhead, R.F., and Jones, G., 2004, Oil, natural gas, and helium
potential of the Chupadera Mesa area, Lincoln and Socorro Counties, New
Mexico: New Mexico Bureau of Geology and Mineral Resources, Open-file
Report 478, 95 p., CD-ROM.
Kues, B.S., 2001, The Pennsylvanian System in New Mexico: overview with suggestions
for revisions of stratigraphic nomenclature: New Mexico Geology, v. 23, p. 103-122.
Lucas, S.G., 1991, Triassic stratigraphy, paleontology, and correlation, south-central New
Mexico: New Mexico Geological Society, 42nd Field Conference, Guidebook, p. 243259.
Lucas, S.G., Krainer, K., and Colpitts, R.M., Jr., 2006, Abo-Yeso (Lower Permian)
stratigraphy in central New Mexico: New Mexico Museum of Natural History & Science,
Bulletin 31, p. 101-117.
Peterson, C., and Roy, M., 2005, Gravity and Flexure Models of the San Luis,
Albuquerque, and Tularosa basins in the Rio Grande Rift, New Mexico and Southern
Colorado: New Mexico Geologic Society, 56th Field Conference, Guidebook, p. 105114.
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